1. Field of the Invention
The present invention relates generally to a lighting apparatus capable of protecting eyesight and, more particularly, to a lighting apparatus capable of protecting eyesight that additionally emits light having wavelengths that are not emitted by existing fluorescent lighting apparatuses, but are essential to the action of eyesight.
2. Description of the Related Art
Various types of lighting apparatuses using fluorescent lamps are used as main lighting apparatuses in public facilities and homes. Meanwhile, fluorescent desk lamps, such as that shown in FIG. 1, are widely used as auxiliary desk lighting apparatuses in study rooms and laboratories.
In the meantime, when 60 Hz home Alternating Current (AC) power is used for fluorescent desk lamps without conversion, the fluorescent lamps flicker 120 times per second, which fatigues the eyes. Accordingly, fluorescent inverter desk lamps, which convert existing 60 Hz AC power into 44 KHz high-frequency power using electronic ballasts equipped with inverter circuits and apply the 44 KHz high-frequency power to lamps, so that the fluorescent lamps flicker 80,000 to 90,000 times per second, thereby preventing the eyes from detecting such flickering, are mainly used at present.
Furthermore, although lighting apparatuses using fluorescent lamps as main lighting lamps sometimes use electronic ballasts which are not equipped with inverter circuits, electronic ballasts equipped with inverter circuits have been used recently.
Meanwhile, since natural light (solar light) has a wide wavelength range of 380 to 780 nm and humans' eyesight is adapted to natural light, humans feel comfortable and, simultaneously, humans' eyesight can be protected when humans view objects that are illuminated with natural light.
Conventional fluorescent lamps are inexpensive (one to three dollar). However, since the fluorescent material applied to the inner glass of the fluorescent lamps is mainly a phosphate, silicate or tungstate compound, large amounts of blue light in a wavelength range of 430 to 450 nm, red-orange light in a wavelength range of 600 to 620 nm and yellow-green light in a range of 530 to 560 nm are emitted, and small amounts of pure red light in a wavelength range of 620 to 700 nm and pure green light in a wavelength range of 498 to 530 nm are emitted, as shown in the upper graph of FIG. 2, and thus the light emitted from the fluorescent lamps is different from natural light, which is composed of red, green and blue colors. Therefore, the conventional fluorescent lamps have problems related to color rendering, and thus they fatigue the eyes when humans' photoreceptor cells are used for a long time.
Meanwhile, humans' photoreceptor cells consist of cone cells and rod cells. The three types of cone cells, which detect color, are relatively sensitive to light at 420 nm, light at 530 nm, and light at 560 nm, respectively, and rod cells are relatively sensitive to light at about 495 nm.
In particular, recent research has proven that cone cells and rod cells participate in vision through interaction therebetween. This means that bluish green light at about 495 nm, to which rod cells, which have not been considered to be important in discerning red, green and blue light based on the conventional theory, in which only cone cells participate in the detection of color, are sensitive and improve sharpness, and thus they play an important role in vision.
However, existing fluorescent lamps emit slight amounts of bluish green light at about 495 nm, and thus they do not provide optimal conditions for the activity of photoreceptor cells.
In brief, the existing fluorescent lamps have problems rendering colors because they emit small amounts of pure red light in the wavelength range of 620 to 700 nm and pure green light in the wavelength range of 498 to 530 nm, and do not improve sharpness because they emit small amounts of bluish green light at about 495 nm.
In order to mitigate the shortcomings of the existing fluorescent lamps, full-spectrum fluorescent lamps, which are constructed by adding a phosphorus compound to fluorescent material for the existing fluorescent lamps and can emit light at red wavelengths, have been invented. However, it is impossible to manufacture them at low cost because the phosphorus compound is a rare material, and thus the material cost is increased, and because the yield thereof is low.